[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus having a transport roller for transporting a transfer sheet between a sheet feeding section and a transfer means, and capable of correcting an oblique transfer state of the transfer sheet. Things.

[0002]

2. Description of the Related Art In a typical image forming apparatus, a transfer sheet fed from a sheet feeding section is conveyed to a transfer means using a sheet feed roller, and a visible image of a photosensitive member is transferred to the transfer sheet to transfer the transfer sheet. To form a desired image.

[0003]

In this type of image forming apparatus, when the transfer paper is fed from the paper feed unit by the paper feed roller, the parallelism between the paper feed roller and the transfer means is not good, Transfer paper is skewed in the slanted feeding direction, that is, it is skewed in the proper feeding direction due to improper setting of the transfer paper in the paper feed section, pressure difference between the left and right of the paper feed roller, or other causes. In such a case, there is a limit in correcting the skew by the registration roller.

Further, when the transfer paper is conveyed by the registration rollers, there is a problem that all the load on the transfer paper in the process from the registration rollers to the paper feeding section must be released.

Japanese Patent Application Laid-Open No. 2-54285 discloses that
A stepping motor is used to drive the photoconductor and drive the transfer paper support / transporter so that the image on the transfer paper and the image on the photoconductor can be aligned with high precision, but the transfer paper is skewed. It is not used to correct the skew when transported.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an image forming apparatus which solves the above-mentioned problems and corrects a transfer sheet which has been fed obliquely to make it correct.

[0007]

According to a first aspect of the present invention, there is provided a photosensitive member, a charger for uniformly charging the surface of the photosensitive member, and an exposing means for projecting image light corresponding to recorded information onto the photosensitive member. Developing means for developing the electrostatic latent image on the photoreceptor, transfer means for transferring a visible image of the photoreceptor onto transfer paper, a paper supply unit for accommodating the transfer paper, and conveyance for conveying the transfer paper from the paper supply unit An image forming apparatus having a conveying unit that conveys transfer paper fed from a paper feeding unit to a transfer unit, a detecting unit that detects a state of oblique feeding of the transfer paper during conveyance, A control drive circuit is provided for correcting the oblique feeding state of the transfer paper by changing the drive of the transport roller unit based on the detection result.

According to the first aspect of the present invention, even if the transfer sheet is skewed during conveyance, the detecting means detects the skewed state and drives the conveyance roller unit based on the detection result. Since the state of the transfer paper is obliquely fed is changed, the skew of the transfer paper can be surely corrected, and the transfer paper can be fed in a correct posture.

According to a second aspect of the present invention, while the transfer paper fed from the paper feeding section is being conveyed, the state of obliquely feeding the transfer paper is detected by the detection means, and the control drive circuit controls the right and left sides of the conveyance roller section. Are separately driven to correct the state of the oblique feeding of the transfer paper. According to a third aspect of the present invention, while the transfer paper fed from the paper feeding unit is being conveyed, the detecting unit detects the state of the skew of the transfer paper, and the control drive circuit detects the skew amount of the transfer paper from the skew amount. The rotational speed control of the left and right drive rollers of the unit is feedback-controlled to correct the state of the transfer paper being skewed. According to a fourth aspect of the present invention, while the transfer paper fed from the paper feed unit is being conveyed, the detecting unit detects the state of the oblique feed of the transfer paper after passing the conveyance roller unit, and the transfer paper is passing through the conveyance roller unit. In addition, the control drive circuit controls the rotational speeds of the left and right drive rollers of the transport roller unit based on the amount of oblique feed to correct the oblique feed state of the transfer paper.

According to a fifth aspect of the present invention, while the transfer sheet fed from the sheet feeding unit is being conveyed, the state of the transfer sheet being skewed is detected by the detecting means, and the control drive circuit controls the right and left sides of the conveyance roller unit. By adjusting the rotation speed of the driving roller by the stepping motor, the state of the oblique feeding of the transfer paper is corrected.

According to the present invention, the control driving circuit can drive the left and right driving rollers of the transport roller unit to correct the state of the oblique feeding of the transfer paper.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an image forming apparatus 1 according to the present invention. As shown in FIG. 1, the image forming apparatus 1 is generally charged uniformly with a photoconductor (drum) 3 and a surface of the photoconductor 3. Charger 5, exposure means 7 for projecting image light corresponding to recording information onto photoconductor 3, developing means 9 for developing an electrostatic latent image on photoconductor 3, and visualization of photoconductor 3 on transfer paper 11 The image forming apparatus includes a transfer unit 13 for transferring the image, a paper supply unit 15 for storing the transfer paper 11, and a conveyance unit 17 for conveying the transfer paper 11 from the first paper supply unit 15 or the second paper supply unit 16.

In the image forming apparatus 1, light is emitted from a light source to an image document, and the reflected light is detected by a light receiving element.
The exposure unit 7 projects image light corresponding to the recording information of the document onto the photoconductor 3 based on the detection signal, and is supplied with toner from the development unit 9 to develop the electrostatic latent image on the photoconductor 3. Next, the transfer paper 11 fed from the paper feeding unit 15 is corrected in skew by the transporting means 17 and in the correct feeding posture, the transfer paper 11 is transferred to the transfer means 13 in synchronization with the toner image on the photoconductor 3. The toner image is transferred.

After the transfer, the transfer material 3 is transferred to the belt transport unit 1
The photoconductor 3 having been transferred by the fixing unit 9 and passed through the fixing unit to fix the toner image, and having been transferred, is uniformly charged by the charger 5 after cleaning by the cleaning unit 21 to prepare for the next electrostatic latent image formation. Next, the transport unit 17 of FIG.
The structure of will be described.

The transporting means 17 includes rollers 25, for transporting the transfer paper 11 from the paper supply unit 15 or 16.
27, a first transport roller unit 29, a second transport roller unit 31,
A registration roller unit 33, a first paper detection sensor 35, a first paper detection sensor 37, and a registration sensor 39 are provided.

A first transport roller section 29 is disposed between the paper supply section 15 and the registration roller section 33, and a second transport roller section 31 is disposed between the paper supply section 16 and the registration roller section 33. . The first paper detection sensor 35 is desirably disposed near the first transport roller unit 29, particularly, immediately after the transport path. The second paper detection sensor 37 is desirably disposed near the second transport roller unit 31, particularly, immediately after the transport path. The registration sensor 39 is disposed immediately before the registration roller unit 33.

FIGS. 2 and 3 show an example of the configuration of the first transport roller unit 29 and the second transport roller unit 31 of FIG. 1. The transfer directions A1 and A2 of the transfer paper 11 are perpendicular to the plane of FIG. It is. First transport roller section 29 and second transport roller section 31
Have the same configuration, and a driving roller system 41 and a driven roller system 43 for the transfer paper 11 and stepping motors 45 and 47,
Control driving circuits 49 and 51 are provided.

The drive roller system 41 and the driven roller system 43 are both a left part, a right part,
They are separated according to the central part. The driven roller system 43 includes a driven roller 43a in a left portion, and a driven roller 43 in a central portion.
b, a driven roller 43c at the right portion, and these driven rollers 43a, 43b, 43c are rotatably supported by bearings 55, respectively, and are driven by biasing means 57 such as a spring or a leaf spring. 41b, 41
Pressure c is applied to pressure c.

The driving roller system 41 has a driving roller 41a at a left portion, a driving roller 41b at a central portion, and a driving roller 41c at a right portion. These drive rollers 41a,
41b and 41c are rotatably supported by bearings 61, respectively, and are independent so that the driving force from the stepping motors 45 and 47 is not applied to the center driving roller 41b. The shafts of the drive rollers 41a and 41c at the left and right positions have driven gears 65 and 67, respectively.
5 and 67 mesh with drive gears 69 and 71, respectively. The drive gears 69 and 71 are attached to output shafts of the stepping motors 45 and 47, respectively. The stepping motors 45 and 47 include control driving circuits 49 and 5, respectively.
A skew angle θ generated in the transfer material 11 as shown in FIG. 4 is corrected by applying a predetermined number of pulses from 1 and performing feedback on the rotational speed control of the left and right drive rollers 41a and 41c. The transfer paper 11 is correctly fed along the directions of arrows A1 and A2.

As shown in FIGS. 1 and 3, immediately after the first transport roller unit 29 and the second transport roller unit 31, a first paper detection sensor 35 and a second paper detection sensor 37 are disposed, respectively. . First paper detection sensor 35 and second paper detection sensor 3
7 has two sensors S1 and S2 on the left and right, respectively, and emits light to irradiate the transfer paper 11 to detect the presence or absence of the transfer paper 11; It has a light receiving unit for receiving light.

Next, the operation of the image forming apparatus 1 will be described.

The transfer paper 11 fed and conveyed from the first paper supply unit 15 shown in FIG. 1 is detected by the paper detection sensors S1 and S2 shown in FIG. You. At that time, the transfer paper 11 is conveyed while being skewed at an angle θ as shown in FIG.
If the right side of 1 is advanced and the left side is delayed, there is a difference in the time when the paper detection sensors S1 and S2 detect the transfer paper 11. The time difference is fed back to the drive control circuits 49 and 51, and the drive control circuits 49 and 51 are driven by the left and right stepping motors 45 and 4 so as to eliminate the time difference.
7 to reduce the rotation speed of the right driving roller 41c or increase the rotation speed of the left driving roller 41a. Thereby, the transfer paper 1
1 is corrected, the skew of the transfer paper 11 is corrected, and the transfer paper 11 is sent in a correct posture.

At this time, the transfer paper 11 is
Since it is desirable that the skew is corrected during the passage of the transfer paper 9, the drive control circuits 49 and 51 have a control ability to end the skew correction within the time when the transfer paper 11 passes.

The transfer paper 11 fed and conveyed from the second paper supply unit 16 shown in FIG. 1 immediately after passing through the second conveyance roller unit 31, is immediately detected by the paper detection sensors S1 and S2 shown in FIG.
Is detected by At this time, when the transfer paper 11 is conveyed while being skewed at an angle θ, for example, as shown in FIG. 4 and the right side of the transfer paper 11 advances first and the left side delays, the paper detection sensors S1 and S2 There will be a difference in the time to detect 11. The time difference is fed back to the drive control circuits 49 and 51, and the drive control circuits 49 and 51 convert the time difference into a command signal of the rotational speed to the left and right stepping motors 45 and 47 so as to eliminate the time difference. Either reduce the rotation speed of the drive roller 41c or increase the rotation speed of the left drive roller 41a. This allows
The transfer speed of the transfer sheet 11 at the left and right positions is corrected, the skew of the transfer sheet 11 is corrected, and the transfer sheet 11 is sent in a correct posture.

At this time, the transfer paper 11 is
Since it is desirable that the skew is corrected during the passage of the transfer paper 1, the drive control circuits 49 and 51 have a control ability to end the skew correction within the time when the transfer paper 11 passes.

With this configuration, even if the transfer paper 11 is skewed while being transported, the skew amount is converted from the detection response time difference between the left and right paper detection sensors S1 and S2.
This is fed back to the drive control circuits 49 and 51, so that the left and right drive rollers 41a and 41c and the driven rollers 43a and 43c
By adjusting the rotation speed of the transfer paper 11, the skew of the transfer paper 11 can be reliably corrected and the transfer paper 11 can be fed in a correct posture. The toner image can be transferred accurately.

By the way, the present invention can be variously modified without departing from the scope of the claims. For example, in the illustrated embodiment, two drive rollers that are actually driven by a stepping motor are provided for simplification of the description and the drawings. Not only one drive roller but also a plurality of drive rollers are required.

[0028]

As described above, according to the first aspect of the present invention, even if a transfer sheet is skewed during conveyance, the detecting means detects the skewed state and detects the state. Since the driving of the driving roller of the transport roller unit is changed based on the result to correct the state of the oblique feeding of the transfer sheet, the skew of the transfer sheet can be surely corrected and the transfer sheet can be fed in a correct posture.

According to the second to fifth aspects of the present invention, the control drive circuit can drive the first drive roller and the second drive roller to correct the oblique feeding state of the transfer paper.

FIG. 1 is a side view showing an embodiment of an image forming apparatus of the present invention.

FIG. 2 illustrates a first conveyance roller unit and a second conveyance unit of the image forming apparatus of FIG. 1;
FIG. 3 is a diagram illustrating a configuration example of a transport roller unit.

FIG. 3 is a diagram illustrating a first conveyance roller unit and a second conveyance roller unit of the image forming apparatus of FIG. 1;
FIG. 3 is a perspective view illustrating a configuration example of a transport roller unit.

FIG. 4 is a plan view illustrating a state in which feedback of rotational speed control of left and right drive rollers is performed to correct a skew angle θ generated in a transfer material.

 DESCRIPTION OF SYMBOLS 1 Image forming apparatus 3 Photoreceptor 5 Charger 7 Exposure means 9 Developing means 11 Transfer paper 13 Transfer means 15, 16 Paper feed section 17 Transport means 29, 31 Transport roller section 35, 37 Detecting means 41a, 41c Driving roller 45, 47 Stepping Motor 49, 51 control drive circuit

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Toshio Shimazaki Ricoh Co., Ltd. 1-3-6 Nakamagome, Ota-ku, Tokyo